1. Field of the Invention
The present invention generally concerns microlenses, electrophoresis, microfluidics, alignment, two-dimensional alignment and microfluidic wells.
The present invention particularly concerns precise control and active positioning of sub-millimeter-sized spherical lenses in two-dimensions through the application of electrophoretic forces in a microfluidic well, including for the active alignment of microlenses to optical fibers, VCSELs, LEDs, photodetectors, etc.
2. Description of the Prior Art
2.1 Electrophoresis and Electrophoretic Forces
The presentinvention will be seen to involve electrophoresis, and electrophoretic forces.
Electrophoresis, which is the motion of a charged particle under an applied DC electric field in an electrolyte solution, has a very robust history in the biological and chemical sciences with such uses as DNA and protein sequencing. See, for example, Hindley, J., Staden, R., DNA sequencing, Elsevier Biomedical Press, New York, N.Y., 1983. Colloidal chemistry is also supported. See, for example, Hiemenz, P. C., Principles of Colloid and Surface Chemistry, chpts. 12–13, Marcel Dekker, 1986.
In the past decade, with the maturation of semiconductor processing and optics technologies, the use of the electrophoretic force has been integrated into the optics and electronics fields producing results such as heterogeneous integration of electrical components using pick-and-place techniques. See Chi Fan, Shih, D. W., Hansen, M. W., Hartmann, D., Van Blerkom, D., Esener, S. C., and Heller, M., “Heterogeneous integration of optoelectronic components”, Proceedings of the SPIE—The International Society for Optical Engineering, vol. 3290, pp. 2–7, Optoelectronic Integrated Circuits II, San Jose, Calif., USA, Jan. 28–30, 1998. See also Esener, S. C., Hartmann, D., Guncer, S., Chi Fan, Heller, M., Cable, J., “DNA-assisted assembly of photonic devices and crystals”, OSA Trends in Optics and Photonics Series, Spatial Light Modulators, edited by: Burge, G. and Esener, S. C., vol. 14, pp. 65–8, Proceedings of Spatial Light Modulators, Incline Village, Nev., USA, Mar. 17–19, 1997.
Further results are reported in the assembling of colloidal particles to produce photonic structures. See Song, J., Sun, H., Xu, Y., Fu, Y., Matsuo, S., Misawa, H., “Three-dimensional photonic crystal structures achieved with self-organization of colloidal particles”, Optical and Quantum Electronics, vol. 32, no. 12, pp. 1295–300, December 2000. See also Hayward, R. C., Saville, D. A., Aksay, I. A., “Electrophoretic assembly of colloidal crystals with optical tunable micropatterns”, Nature, vol. 404, no. 6773, pp. 56–9, March 2000. See also Younan, Xia, Gates, B., Sang Hyun Park, “Fabrication of three-dimensional photonic crystals for use in the spectral region from ultraviolet to near-infrared”, Journal of Lightwave Technology, vol. 17, no. 11, pp. 1956–62, November 1999.
Still further key research is reported in the relatively new fields of Optical MEMS and Bio-MEMS. See M. Ozkan, C. Ozkan, O. Kibar and S. Esener, “Massively parallel low cost pick and place of optoelectronic devices via electrochemical fluidic processing”, Optical Letters, September 2000. See also M. Ozkan, C. Ozkan, O. Kibar, M. Wang, S. Bhatia and S. Esener, “Heterogeneous Integration of Biological Species and Inorganic Objects by Electrokinetic Movement”, IEEE Journal of EMB Magazine, in press, 2001. See also M. Ozkan, O. Kibar, C. Ozkan and S. Esener, “A new optical and electric-field assisted fluidic technique for pick and place of electronic devices”, OC'2000, Quebec, Canada, Jun. 18, 2000.
Up to now, research using electrophoresis has mainly focused on sub-micron particles and has not particularly been extended into tens to hundreds of micron-sized particles, where the electrophoretic force can still be quite strong.
2.2 Optical Interconnects and Microlenses
The present invention will be seen to be of use in optical interconnects using, inter alia, active alignment of microlenses.
One of the key technology hurdles to optical interconnects has been the accurate alignment of microlenses for the collimation or focusing of directed beam sources. For individual laser sources or single optical fibers, current technologies such as photoresist reflow and microjet printing are widely known and have produced high quality microlenses, but these technologies have a distinct limitation when fabricated in an array form. The requirement of high precision in the initial alignment of the lens array and the fixed pitch spacing of these lenses make it extremely difficult to compensate for variations in the individual source locations that can occur over time, i.e. through mechanical vibrations, or from one array to another, without dramatically increasing the size of the microlens.
One solution to this problem would be an electrically addressed array of microlenses that permitted individual alignment of each lens to its corresponding source. The present invention will be seen to support this.